Micro-microwave generator



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March 9, 1954 Filed Feb. 11, 1944 l I OSCILLATOR' AMPLIFIER z H 0 I.

. llll J. M. CAGE MICRO-MICROWAVE GENERATOR 2 Sheets-Sheet l INVENTOR.dHA/M 6465,

March 9, 1954 CAGE 2,671,857

MICRO-MICROWAVE GENERATOR Filed Feb. 11, 1944 2 Sheets-Sheet 2OSClLLATPR VIM/v.44. C465,

Patented Mar. 9, 1954 UN I TED STAT ES FAT EN T OFFICE 2,671,857MICRO-MICROWAVE GENERATOR John M. Cage, Upper Montclair, N. J.Application February 11, 1944, Serial No. 521,950

5 Claims.

This invention relates generally to electromagnetic wave generators,particularly for the wave length region between presently knownmicrowaves, on the one hand, and infra-red on the other, or in otherwords, in the mega-megacy'cle region. The present invention may becharacterized generally as dealing with improvements and refinements inthe type of micro-microwave generator disclosed in my copendingapplication entitled Radiovision System, filed August -30, 1943, SerialNo. 500,577. As more fully disclosed in said copending application, sucha generator is employed in a system designed to detect or visualizeobjects obscured by darkness, fog, dust, haze, or the like, thegenerator being utilized, for instance, to direct a beam of generatedwaves of micro-micro dimensions to the field of view, and a suitablereceiver device being provided which is designed to respond to raysreflected back from objects in the field of view. Or, as anotherinstance, the receiving device may respend to a beam received directlyfrom the generator; for example, a receiver carried by an airplane mayreceive waves radiated from generators outlining or indicating a landingstrip.

The generator comprises, generally speaking, a multiplicity of minutemetal particles mounted on an insulation base, and periodically chargedby a suitable high voltage, and then permitted to discharge. During thedischarge, the particles oscillate at their own resonant frequency, andin this oscillating state, generate micro-microwaves which may bereflected or beamed to the field of view. The particles oscillate at aresonant frequency governed by their size, and it is hence possible togenerate micro-microwaves of various wave lengths by choosing particlesizes of various gradings. A particle size of approximately one hundredmesh results in generated frequencies of approximately two millionmegacycles', such as are suited to the purposes at hand, being notseriously interfered with by fog, snow, and the like. is given, orcourse, as merely typical of the invention, and not as limitativethereoi i.

The general object of the present invention is the provision of animproved and relatively highpower micro-microwave generator of the typeindicat'ed.

With this brief preliminary outline of the subject in mind, theinvention, including its various specific objects, features, andaccomplishments, will be most readily understood by referring to theaccompanying drawings and detailed description, disclosing one presentpreferred and illustrative embodiment thereof.

In the drawings:

Fig. l is a diagram showing one form of improved generator and anenergizing therefor;

Fig. 2 is a longitudinal section through the generator, the View beingsomewhat diagrammatic in nature;

Fig. 3 is a detailed sectionon line ti 3 oi 2';

Fig. 4 is a vertical sectional view 'snownrg the generator tube mountedWithin a parabolic re-- fie'c'tor;

Fig. '5 shows a modified generator aha energiz ing system;

Figs. 6 and 7 show further modified generators in accordance with theinvention; and

Figure -8 is a section on line B -8 of Figure 'l.

Referring first to the embodiment of 14, the generator includes agenerator tube 'll) com prising an evacuated envelope H widen mounted afil'ainent {2, a grid l8, a'plate or anode l4. overlying the plate is aninsulation element I 5, and mounted on the latter, on itsrace away fromthe plate It, is a layer [6 of fine metal particles or filings, arrangedto be insulated frorn one another. 'lihe wave length that will be generated depends largely upon the particle size and hence may be varied tosuit requirements by choice of the particle size employed. Using, Alnicometal and a particle size of amino ima'tely the order or one hundredmesh, I have roduced wave lengths in the approximate region of 153 mu,or in other words, of around two million megacycles. (ionta'caing andconnectedto this layer of metal particles is a connector trip or elementII. By means presentl to be described, a high voltage is periodicallybetween the plate M and the connector strip H, whereby the particles aresubjected to a voltage gradient and hence become charged. Each metalparticle becomes in effect a part of a condenser plate, and thus assumesa high charge. When the charging voltage is subsequently dropped orinterrupted, the particles dis charge and are setinto a state ofoscillation, generating the desired micro-microwaves, which are pickedup and utilized as later to be described.

In Fig. 2, I have shown a present preferred form of generator tube inaccordance with the invention, which will now be described in moredetail. The filament 12, as indicated, of a double helic'ally woundtype, and has leads 2i and 22 extending through the base end of theenvelope H. The grid l'3 is illustratively shown as comprising a helix,mounted on supports 23 and M, to one of which is connected a grid lead25' extending through the base end of the envelope. The plate I4comprises a sleeve surrounding the grid, and mounted on supports 28,which extend through the head end of the envelope and have connectedthereto the plate lead 29. The insulation element I5 illustrativelycomprises a sleeve mounted on the cylindrical plate l4, and this sleevemay be made of a suitable ceramic substance such as porcelain. The metalparticles are mounted on the exterior surface of the sleeve [5. They maybe imbedded directly in the surface of the sleeve, or cemented theretoin any suitable manner. For instance, they may be mounted on the sleeveby incorporating them in a coating of glaze applied thereto. Onepreferred method of producing the layer consists in spraying the ceramicsleeve with a solution of colloidal silver and then firing below themelting point of silver, no glaze being used. The metal particles of thefinal layer are closely spaced from one another, or in contact; they maybe regarded either as surface insulated from one another, or as inconductive relation with one another, but with small resistances betweenparticles.

The particle connector element or strip I! which is in electricalcontact with the particle layer, extends lengthwise of the sleeve [5 andcontacts or overlies a band of particles It. It may be sealed to theceramic sleeve by a coat of glaze. The connector strip l! is connectedby a short lead 30 to a support 3| mounted in the base of the envelopeand provided with an exterior connection lead 32. I

The power of the generator is increased by use of a metal plate 36extending longitudinally along the outside of the sleeve l5 at a pointdiametrically opposite from the connector strip l1, and it is mounted onand electrically connected to the particle layer It by means of aconnector strip 31, which may be similar to the connector strip l1. Thisconnector strip 3! and the plate 36 are not connected to the externalcircuit.

The present illustrated energizing system for the generator tube isshown more particularly in Fig. 1. The filament leads 2| and 22 areenergized from the secondary of a step down transformer 40, the primaryof which may be supplied with current from a 120 volt line. As hereshown, the secondary of this transformer is center-tapped and connectedto the lead 32 which connects with particl layer connector strip I1.

The external plate and particle connector strip leads 29 and 32 aresupplied with a suitable source of high direct current voltage, forinstance, twenty-five to thirty kilovolts. This direct current power maybe obtained from any suitable source, as for instance from a suitablerectifier, such as the one conventionally indicated generally by thenumeral 42.

An oscillator 50, for instance of 100 kilocycles, though this is not tobe taken in a limitative sense, has its output amplified by a suitablevacuum tube amplifier 5|, and the output terminals of the latter areconnected one to generator grid lead 25, and the other to particleconnector strip lead 32. The oscillator 50 is preferably either of asaw-tooth or square wave type, producing steep wave front voltage waves,or in other words, producing voltage changes within minimum timintervals.

The direct current power supply 42 normally impresses a high voltagebetween the plate M of the generator tube and the particle connectorstrip l7, thus subjecting the metal particles to an extremely highvoltage gradient, and causing them to be charged to high potentials.This charging voltage to which the metal particles are subjected isperiodically varied in accordance with the output of the oscillator 50,which will be seen to be improssed across the filament I 2 and grid l3.

When the grid voltag relative to the filament (governed by the amplifiedoscillator voltage) swings more negative, th filament to plate spacecurrent of the tube is decreased or interrupted, and the full D. C.charging voltage is impressed between the plate and particle layer [6.When the grid voltage then swings back (becomes less negative or morepositive) a substantial space current flow from filament to plate, andit will be seen that this space current flow is in parallel with thecondenser formed by the plate and particle layer, with the result thatthe voltage drop across the latter is substantially decreased, so thatthe charged particles are permitted to discharge, and are thus set intooscillation. By employing an oscillator 50 of saw-tooth or square Wavecharacteristics, the voltage impressed between the charging plate andthe particle layer can be increased and/or decreased within minimizedtime intervals. I have found it of advantage to charge the particleswith a relatively steep front voltage wave, and it is likewise ofadvantag to discharge the particles by removing the charging voltage ina minimum time interval. Obviously, use of a saw-tooth Wave will permitthe particles either to be charged or discharged with a steep sidedWave, and use of a square wave oscillator will permit both.

The plate 36 acts as a kind of capacitor or energy distributing element,which tends to cause an equal distribution of potential over the periphery of the particle surface, and is found in practice to increasethe radiation from the generator.

The generator tube of Fig. 2 is shown in Fig. 4 as mounted within aparabolic reflector 60, being understood to be located with its particlelayer in the region of the focal point of the refiector. The reducedrearward end portion of the tube is shown as fitted within an apertureat the back of the reflector, While the plate lead 29 is shown aspassing through the wall of the reflector by means of an insulator 6 I.l

The discharging metal particles of th particle layer I6 are set intointensive oscillation, as previously described, and the frequency ofthis oscillation will vary depending principally upon particle size, allas heretofore described. The oscillating particles generatemicro-microwaves" which are radiated therefrom, and these are reflectedby the parabolic reflector 60 and beamed to the field of vision.

It will be evident that my wave generator is in the nature of acondenser, comprising a condenser plate mounted adjacent one face of aninsulation layer and another condenser plate in the form of a particlelayer applied to the opposite face of said insulation layer, directlyopposite the first-mentioned plate. A connector element then contactsthe particle layer. By this arrangement the condenser structure of thegenerator has a maximum capacity, a maximum potential gradient isestablished, and each particle assumes a large charge. Each individualparticle is charged proportionately to the potential difference betweenthe plate and the particle. The resistance between particles isrelatively small, and under the high charging voltage, electricalactivity oscillating over the particle layer aa'rnesm or over or betweenthe particles, i. e., electricity jumping: from particle. to particle;may. be; ob.- served. during both. charge and discharge.

The charging system for the generator may be or. various types, such iorinstance; as that. closed in. my: copending. application. entitled Ra.-d'iovisionsystem, SerialNo. 500,577, filed August 30-, 194431,. in.which case. a space. current not. being required, the evacuated envelopenught be omitted. Other typical. modifications in both the chargingsystems and the generator will now be described.

Fig. shows schematically a generator without an envelope, and a modifiedcharging system. The generator comprises an insulation sleeve 50, on theoutside surface of which is alayer 5| of metal particles forming oneplate. of the condenser structure. The other plate consists of. ametallic sleeve 52 contacting the inside surface of sleeve 50.Contacting particle layer 5| is a metallic connector strip 53, whilediametrically opposite from the latter is a metallic strip 54 carrying aplate element 55, the latter elements not being connected into theexternal circuit- A suitable source of direct current power is provided,here being shown as in the form of a rectifier-filter combination 5B.The positive output terminal of the latter is connected by a lead 51 tothe plate 60 of a triode Bl. The negative output terminal of the DCpower supply is connected by lead 64 to plate 52. An oscillator 65,preferably either square wave or saw-tooth, has one output terminalconnected by lead 66 to the grid 61 of triode BI, and its other outputterminal connected by lead 68 to the filament or cathode 69 of saidtriode. A C-bias battery may be provided in the filament-grid circuit ofthis triode, as indicated. Particle layer contact strip 53 is connectedby lead H to cathode lead 68, which is grounded.

The wave generator will be seen to be included as a condenser in seriesin the plate circuit of triode 6|. The output saw-tooth or square wavefrom oscillator 65 impressed on the grid of the triode controls thetotal voltage and causes abrupt voltage changes across the generator,which periodically charge the particles of the layer 5| and permit saidparticles to discharge at their resonant frequency.

I have also shown in Fig. 5 the optional use of a variable tuninginductance connected across the condenser structure of the generator.This inductance permits the generator circuit to be tuned to resonance,whereby an optimum delivery of power from the generator may be gained.

I have now disclosed one case (Figs. 1-4) wherein the generator isenclosed in an evacuated envelope, and a second (Fig. 5) wherein thegenerator is not so enclosed. Enclosure in an evacuated envelope, whilenot essential, is advantageous in that under such conditions theparticles will accept a higher charge before discharge takes place. Onthe other hand, use of a generator enclosed within an envelope in whicha small amount of gas, like neon, is introduced is advantageous becauseof lowered resistance between particles, which is conducive to increasedduration of the oscillatory discharge.

In Fig. '6 I have disclosed a modified generator enclosed Within a glassor ceramic envelope 80, which may be either evacuated, or gascontaining. This envelope is here illustratively shown as in the generalform of a parabola, with a 6; closed tnontwal'l 8t... 'I-heinside of theparaboliir sidezwalLM iscoatediwith' alayerlnot metazli. particles,which are. contacted toward the front end wall. of. the envelope by ametallic band 84:. corresponding to the plate at of. Fig. 2; A.- com.tact. button; 85: at the: rearward end. of the en: velope: makes.connection with the; particle layer". and anoutside; metallic; plateor'shell $6} contacts the, outside. surface. of the parabolic side wall.The external connections 81 and 88 are made to button 85. and shell as,respectively. It willbe evident that the genera-tor of Fig. (imay beused, for example, in such a circuit as is shown in 1 Fig. 5.

Finally,- in Figs; 7 and 8-, I- have shown asimplified but-elfectivegeneratorstructure in accordance with the invention, comprising a flatinsulation plate ametallic condenser plate, 91" contacti'ng one surfacethereof, a particle layer 92 contacting the opposite surface thereof,and a contact strip 63 extending transversely across the center of layer92 and making contact therewith. Metal strips 94, parallel to strip 93,contact the upper and lower edges of the particle layer. Externalconnections 95 and 96 are made to strip 93 and plate 9!, respectively.It will be evident that here again, as in each of the earlier describedembodiments, the particle layer comprises one plate of a condenserstructure, whereby the individual particles may be charged to optimumpotentials, and will hence deliver optimum power upon resonantdischarge.

The invention has now been described by way of a specific disclosure ofseveral present illustrative embodiments thereof. It will be understood,however, that this is for illustrative purposes only, and that variouschanges in design, structure, and arrangement may be made withoutdeparting from the spirit and scope of the invention or the appendedclaims.

I claim:

1. A wave generator embodying an insulation layer, a layer of metalparticles adjacent one face of said insulation layer, a metal plateadjacent the opposite face of said insulation layer, and a connectorelement overlying and contacting said particle layer immediatelyopposite an area of said plate.

2. A wave generator embodying an insulation sleeve, a layer of metalparticles adjacent one face of said sleeve, a cylindrical metal plateadjacent the opposite face of said sleeve, and a connector elementoverlying and contacting said particle layer immediately opposite saidcylindrical plate.

3. A wave generator embodying an insulation layer, a layer of metalparticles adjacent one face of said insulation layer, a metal plateadjacent the opposite face .of said insulation layer, a connectorelement overlying and contacting said particle layer immediatelyopposite an area of said plate, and an evacuated envelope enclosing saidmembers.

4. A wave generator system embodying a layer of metal particles, ametallic connector element contacting said layer, a plate parallel tobut spaced from said layer, an electronic tube including anode, grid andcathode elements, an anode circuit for said tube including a source ofdirect current power and said plate and connector element in series anda source of alternating current impressed across the grid and cathodeelements of said tube.

5. A wave generator system embodying a layer of metal particles, ametallic connector element contacting said layer, a plate spaced andinsulated from said layer, a tuning inductance connected between saidconnector element and plate, an electronic tube including anode, gridand cathode elements, an anode circuit for said tube including a sourceof direct current power and said plate and connector element in seriesand a source of alternating current impressed across the grid andcathode elements of said tube.

JOHN M. CAGE.

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